just by pressing a button without the sea horizon to turn to,we should know clearly the relationship between the accuracy of zenith distance observed and the accuracy of a position fixed,the causes of the errors of zenith distance observed,what accuracy of zenith distance observed could be obtained and what accuracy standard should be used.

The paper expounds the principle and the method of measuring zenith distance for celestial positioning based on the direction of gravitational force line.

The pipe driving construction method characteristics,pipe material choice,pipe driving force calculation and apex distance determination,working pit and receiving pit selection and size determination were analyzed.

Quantitative wheel base adjustment mechanism can achieve test bench wheel base adjustment arrival location one time.

The author of this paper presents a group of formulas for designing optimally the wheel base of a hauling automobile and the span length of a trailer, on basis of analyzing and studying systematically wheel bases of hauling automobiles at home and abroad and span lengths of trailers at home and abroad by means of Structural Mechanics, Automobile Structur Caurse and Automobile Theory Course.

According to the analysis on calculation,the following can be worked out,such as the choice of wheelbase,the determination of wheel tread,the setup of power assembly and other major assemblies,the decision of crosswise stabilizing bar,the control of shimmy and so on,which must be taken into consideration to rationa.

It also provides the functions of measuring car-speed and wheelbase, and classifying the automobile automatically.